Myogenic tissue culture systems provide extremely useful model systems in which to study gene regulation during tissue formation. We have isolated and characterized a variety of muscle specific and house-keeping genes that are differentially expressed during myogenesis. These include the genes for alpha skeletal, alpha cardiac, and beta cytoplasmic actin, and the myosin light chain 1- 3 gene. The cis acting sequences responsible for the tissue specific regulated expression of these genes has been characterized and we are in the process of identifying proteins that interact with these regulatory regions. PC12 cells undergo neuronal differentiation in response to NGF. We have isolated the full-sized cDNA and corresponding gene for an mRNA sequence that is induced 50-80 fold in response to NGF. Antibodies to the polypeptide, prepared with lac fusions and various ORFs in the cDNA, demonstrate the protein induction in vitro and its localization in various neuronal tissues in vivo. Preliminary studies suggest that the promoter of this gene responds to NGF induction when joined to a reported gene (CAT). Regulation of this gene and identification of the protein are under study.